Question

A disc is of mass $M$ and radius $r$. The moment of inertia of this disc about an axis tangential to its edge and in the plane of the disc is $\frac{x}{y}M{r}^2$.
Find $(x-y)$.$\left(\text{where x and y are co-prime}\right)$

Answer 1

$I_{1-1}=I_{cm}+M{r}^2$
$I_{1-1}=\frac{1}{4}M{r}^2+M{r}^2=\frac{5}{4}M{r}^2$
$x-y=5-4=1$
Final Answer: $\left(1\right)$